FIG. 1 is a diagram showing system architecture of a Long Term Evolution (LTE) system in a 3rd Generation Partnership Project (3GPP) cellular mobile system. The LTE system includes: a Mobility Management Entity (MME) and a Serving Gate Way (SGW) on a core network side, and User Equipment (UE) (also called as a terminal) and a base station (for example, an eNode B (eNB)) on a radio access network side. An interface between UE and eNB is Uu air interface (or called as air interface for short). An S1 interface is an interface between an eNB and a packet core network, where S1 for the control plane (also called as S1-MME for short) is an interface between the eNB and the MME, while an S1-User plane (S1-U) interface is an interface between the eNB and the SGW. An S11 interface is an interface between the MME and the SGW. An X2 interface is an interconnecting interface between eNBs. An X2-User plane (X2-U) interface and an X2-Control plane (X2-C) interface are interfaces between eNBs.
FIG. 2 to FIG. 5 are schematic diagrams of control plane and user plane protocol stack architectures between a UE, eNB and core network (an MME and an SGW) in an LTE system and a control plane and user plane protocol stack architecture between eNBs in an LTE system. An S1 interface is an interface between the eNB and a packet core network. An X2 interface is an interconnecting interface between eNBs. A Media Access Control (MAC) layer mainly provides data transmission for an upper-layer logical channel, and is responsible for allocating Uplink (UL) and Downlink (DL) radio resources to realize functions such as a Hybrid Automatic Repeat Request (HARQ), scheduling, priority processing, Multiplexing (MUX) and the like. A Physical (PHY) layer mainly provides PHY related signal processing, transmission means and air interface signal conversion for a MAC Protocol Data Unit (PDU) of a data packet from a transmission channel. In addition, an upper protocol Radio Link Control (RLC) layer of a Uu air interface mainly provides fragmentation and retransmission service for user and control data. A Packet Data Convergence Protocol (PDCP) layer mainly completes transmission of user data for an upper layer of user plane or Radio Resource Control (RRC). An RRC layer mainly completes broadcast, paging, RRC connection management, radio bearer control, a mobility function, terminal measurement reporting and control and the like. The abovementioned contents may all be queried in a public 3GPP website. The STCP in FIG. 2 is an abbreviation of Scalable Transmission Control Protocol (TCP), and the GTP is an abbreviation of General Packet Radio Service Tunneling Protocol.
Before Release-10 (Rel-10) of an LTE system, a UE and an eNB may perform UL and DL communication only within a cell configured on one licensed carrier to implement data sending and receiving on the single licensed carrier. In this situation, the eNB may configure only one serving cell for the UE. From Rel-10 of the LTE system, for increasing a peak rate of the UE, radio resources between multiple licensed carrier cells may be dynamically collaborated and utilized, and the UE and the eNB may perform UL and DL communication within cells configured on multiple licensed carriers to implement data sending and receiving on the multiple licensed carriers. In this situation, the eNB may configure multiple serving cells for the UE, including a Primary Cell (Pcell) (a single serving cell bearing Physical Uplink Control Channel (PUCCH) feedback) and multiple Secondary Cells (Scells) (serving cells at least supporting Physical Downlink Shared Channel/Physical Uplink Shared Channel (PDSCH/PUSCH) data transmitted). This is an LTE Carrier Aggregation (CA) technology. However, the LTE CA technology is temporarily limited to aggregation of licensed carriers, a UE supports aggregation of at most 5 licensed carriers, and a maximum aggregate bandwidth is 5×20 M=100 M.
Since licensed carrier resources in a licensed band of an LTE system are relatively deficient (operating companies need to competitively bid for purchasing) and homogenous deployment networking of macro cells under a macro eNB cannot meet an increasing requirement of an LTE user on heavy service traffic, an LTE operating company is expected to develop and utilize unlicensed carrier resources in an unlicensed band (operating companies do not need to competitively bid for purchasing and multiple operating companies can freely compete for preemption and use the unlicensed carrier resources), and homogenous deployment networking of micro cells under a micro eNB or a Lower Power Node (LPN) is expected to be adopted for coverage of a service hotspot, such as a region with a dense population flow. FIG. 6 is a schematic diagram of configuring two macro cells which have roughly the same UL and DL radio coverage and are located on two different adjacent licensed carriers in the same licensed band respectively for a CA operation. A UE may simultaneously perform UL and DL communication with the macro cells on the two licensed carriers within effective coverage to implement data sending and receiving on the double licensed carriers. In FIG. 7, two LPN micro cells are added on the basis of FIG. 6, and the two LPN micro cells are located on two different unlicensed carriers in an unlicensed band respectively, and keep timing synchronization with the two macro cells in FIG. 6 by ground optical fiber collaboration. The macro cells on the two licensed carriers and the micro cells on the two unlicensed carriers may theoretically be configured for the CA operation together, and the UE may simultaneously perform UL and DL communication with the macro cells on the two licensed carriers and the micro cells on the two unlicensed carriers within effective coverage to implement data sending and receiving on multiple carriers.
FIG. 8 is a working architecture of pure licensed CA of LTE. When an eNB or a UE serves as a sender, N parallel HARQ entities may be configured in a MAC entity, and N HARQ data packets (or called as MAC PDUs) generated under a specific Transmission Time Interval (TTI) are finally converted into LTE specific physical waveform signals after a series of related processing (for example, channel coding, modulation and resource block adaption mapping) of a PHY entity and the LTE specific physical waveform signals are sent on N licensed carriers. A UE or eNB serving as a receiver performs reverse processing through the MAC/PHY entity. Here, a single Pcell and N−1 Scells are all configured on the licensed carriers.
FIG. 9 is a working architecture of unlicensed CA of LTE. When an eNB or a UE serves as a sender, N parallel HARQ entities are configured in a MAC entity, where some of the N parallel HARQ entities are conventional HARQ entities serving licensed carriers (the same as the HARQ entities in FIG. 8), while the others are U-HARQ entities serving unlicensed carriers (transformation and enhancement may need to be performed on the conventional HARQ entities for characteristics of the unlicensed carriers). N generated HARQ data packets (or called as MAC PDUs) are finally converted into LTE specific physical waveform signals after a series of related processing (for example, channel coding, modulation and resource block adaption mapping) of a PHY entity, where some of the LTE specific physical waveform signals are sent on the licensed carriers, while the others are sent on the unlicensed carriers. Similarly, the PHY and Unlicensed PHY (U-PHY) entities are distinguished here to identify differences from a conventional PHY entity. Here, there is still a single Pcell on a licensed carrier and a plurality of Scells on the licensed carriers, as well as a plurality of Unlicensed Scells (U-Scells) on the unlicensed carriers.
Since resources on an unlicensed carrier are randomly shared by multiple eNBs/Wireless Fidelity (WIFI) Access Points (APs) of multiple same operating companies/different operating companies in a certain PHY local region, each eNB monitors a busy or idle state of a detection channel in a Listen Before Talk (LBT) manner, and then tries to preempt the channel resources on the unlicensed carrier. For example, in the same serving region, an eNB1 of an operating company 1 configures CA as Pcell1+U-Scell for UE1 under the eNB1, and an eNB2 of an operating company B configures CA as Pcell2+U-Scell for UE2 under the eNB2. The Pcell1 and Pcell2 are located on respective licensed carriers of the operating company A/B respectively, and have no interference conflicts and channel resource sharing problems. However, the U-Scells are located on the same unlicensed carrier, and under this condition, every time when the respective eNBs of the operating company A/B are intended to send data, whether the unlicensed carrier is occupied by another eNB/WIFI AP/UE and the like or not may need to monitored first. For example, when received energy, detected by executing Clear Channel Assessment (CCA) by the eNB1 at a certain periodic time, on a full bandwidth of the unlicensed carrier is more than a certain threshold, it represents that the unlicensed carrier has been occupied at the present moment, and the eNB1 may not preempt a channel resource on the unlicensed carrier, otherwise strong interference to the other node may be formed. Thereafter, the eNB1 usually waits for a period of time (back-off time), and the eNB1 executes CCA detection of a next round to try to preempt the resource on the unlicensed carrier again at a next specific time. When the received energy, detected by executing CCA detection by the eNB1, on the full bandwidth of the unlicensed carrier is lower than a certain threshold, it represents that the unlicensed carrier is idle at the present moment, and the eNB1 may independently occupy a period of Channel Occupancy Time (COT) for Physical Downlink Control Channel (PDCCH) UL and DL scheduling and PDSCH data block sending or PUSCH data block receiving similar to those on a licensed carrier, and then may release the occupied unlicensed carrier channel resources.
In a radio environment where multiple nodes such as eNBs/WIFI Aps/UEs of the same/different operating companies in the same local region complicatedly coexist, the eNBs may successfully preempt local unlicensed carrier channel resources and execute DL data block scheduling, but it does not mean that the UE can certainly reliably receive. This is because there may exist some hidden nodes around the receiving UE, these hidden nodes may not be able to perceive certain reserve signals of the sending eNB (their CCA detection results for local surroundings also indicate an idle state of the detection channel), various transmitted signals of these hidden nodes may also not be strongly perceived by the sending eNB but may form strong receiving conflict interference to the receiving UE, and the UE may hardly correctly demodulate data blocks from the serving eNB. As shown in FIG. 10, after an eNB successfully preempts an unlicensed carrier channel resource and sends PDCCH DL scheduling and a PDSCH data block, a UE may not correctly receive and demodulate the PDSCH data block due to existence of strong interference (a part shown by the ellipse in FIG. 10) of a hidden node on a UE side, and then feeds back a receiving and demodulation failure Negative Acknowledgement (NACK) through a PUCCH on a licensed carrier after a specific time period. Therefore, for implementing DL data block transmission of a relatively high success rate, a relatively safe method is as follows. When a sending eNB successfully preempts local unlicensed carrier channel resources, a receiving UE can also preempt and occupy local unlicensed carrier channel resources at the same time, so as to form resource protection on both sending and receiving parties. Similarly, for implementing UL data block transmission of a relatively high success rate, a relatively safe method is as follows. When a sending UE successfully preempts local unlicensed carrier channel resources, a receiving eNB can also occupy local unlicensed carrier channel resources all the time (which is still implemented by locally sending a certain reserve signal, as shown in FIG. 11). According to a related technology, for example, during DL transmission, in order to avoid potential strong interference of a hidden node on a UE side, an eNB may send a certain DL collision probe command or another similar pre-scheduling-driven auxiliary signal before a DL data block is formally scheduled, a UE starts performing CCA detection on a local radio environment after receiving the probe command until it is detected by CCA detection that a local unlicensed carrier channel resource of the UE is idle, and then the UE may give an UL feedback to notify the eNB that the UE side has gotten ready to reliably receive the DL data block. Thereafter, the eNB starts normal DL scheduling and data block sending only after determining that there is no strong interference of the hidden node on the UE side. Such a collaboration manner requires the eNB/UE to perform advance collision probe and feedback loopback for one time or many times before each formal data packet transmission, and also requires the sending eNB to reserve and occupy the local unlicensed carrier channel resource for a long time during conflict probe loopback (for preventing the unlicensed channel resource of the sending eNB from being preempted by another competitive node). Such a manner may require relatively large amount of control signaling, and may have large resource overhead waste and data packet scheduling delay.
For the problem of relatively large resource waste and data packet delay caused by the fact that an eNB/UE may need to perform conflict probe and feedback loopback for many times and the eNB may need to reserve and occupy a local unlicensed carrier channel resource for a long time during conflict probe loopback, there is yet no effective solution.